This one needs a full page to itself. It can pull code directly from stackoverflow, github, etc... and display it directly on the search page.

It has AI driven, has a nice side bar to easily read the answers, and can be sent to YouChat for better answers. It can also integrate with a few other sites if you log in. You.com has a lot more apps for code, and tons of other stuff. 

Other apps of notable mention are Code Complete, Geeks for Geeks, and the Regex creator. At the time of writing this, the only good way to interact with a collection of apps, is to make an account, "pin" the apps you like from the app store, and on the main page, click "More" and select pinned.